The present invention relates to a method of producing a single-core cord of reinforced optical fiber having a new structure.
A single-cord cord of optical fiber has such a basic structure that the core and clad made of quartz glass or the like are covered with a buffer layer as the primary coating and a reinforcing layer as the secondary coating formed on the buffer layer.
The buffer layer is usually made of silicone rubber and the secondary coating is made of nylon or FRP (fiber-reinforced thermosetting resin). The resin matrix of FRP is usually an unsaturated polyester containing general-purpose styrene polymer on account of its ease of use and its low price. It was however found by experiments made by the present inventors that styrene monomer, during the manufacturing process of the cord, migrates into the buffer layer of silicone rubber to swell it and cross-links in the buffer layer to make it turbid. Thus styrene has the possibility of impairing the buffering function of silicone rubber.
The present invention was completed to solve the above-mentioned problem. Accordingly, it is an object of the invention to provide a method of producing a single-cord of reinforced optical fiber having a new structure. Particularly, an object of the invention is to provide a method of producing single-core cord of reinforced optical fiber in w hich a buffer layer may be protected from becoming turbid and from losing its buffering function, thereby reducing transmission loss.
Another object of the invention is to provide a method of producing a reinforced optical fiber having an increased strength.